The possibility to chemically characterize the metabolic fingerprint of a subject is a very important innovation in medical science. To this aim different analytical approaches can be employed and each one has advantages and disadvantages and so it is important to make a correct choice in order to give an accurate and reproducible response. Technologies based on chromatography or sensors are the main groups and the principal difference is related to the possibility to make a correct recognition and quantification of all the molecules in the sample or to have a qualitative and general information about a family of volatile organic compounds (VOCs). In the present chapter a brief overview of the principal analytical approaches employed in chemical characterization of gaseous samples will be made.